Last summer, Welty began to map the locations of peaches, apricots, walnuts, mulberries and plums he found along the streets of Boulder, Colorado. "In March, he and Caleb Philips, a professor of computer science at the University of Colorado, expanded that database into Falling Fruit, a website that catalogs more than half a million urban trees with edible products," reports Henry Grabar. "In the two-dozen cities where Welty and Philips have obtained municipal planting data or teamed up with local foragers, there is something to eat on nearly every corner."

"Welty hopes urbanites will begin to see the nutritional value in their surroundings," says Grabar. "All the momentum behind urban foraging will drive the planting of fruit trees," he imagines. "Maybe we could begin to build more edible cities deliberately."